Dewaxing hydrocarbon oil



Patented Sept. 15, 1936 DEWAXING HYDROCARBON OIL Edwin C. Knowles, Beacon, N. Y; assignor to The Texas Company, New York, N. Y., a corporation of Delaware No Drawing. Application May 11, 1935, Serial No. 20,989

4 Claims.

This invention relates to dewaxing hydrocarbon oil and more particularly to the removal of wax from mineral lubricating oil stock for the production of low pour test lubricating oils.

The invention contemplates a solvent dewaxing process wherein a solvent selected from the dialkyl ethers of ethylidene is employed, such as dimethyl, diethyl and dipropyl ethers of ethyl idene.

These compounds have the following chemical structure where R, is an alkyl radical from methyl to propyl inclusive:

/OR CH3CH\ More specifically the invention comprises mixing wax-bearing mineral oil with a solvent comprising ethylidene diethyl ether or acetal in proportions such that at temperatures of F. and below the solvent has substantially complete solvent action on the liquid constituents of the oil and substantially no solvent action upon the solid waxy constituents of the oil. This mixture is chilled to temperatures of the order of 0 F. and below, depending upon the desired pour test of the dewaxed oil, to precipitate the wax constituents. The precipitated wax constituents are then separated from the cold mixture by mechanical means, such as filtering, centrifuging or settling.

I have discovered that the dialkyl ethers of ethylidene, such as acetal, possess properties which render them suitable as dewaxing solvents. Acetal, for example, has anti-solvent properties for paramn wax and in addition possesses comparatively high solvent power for mineral oil so that it may be employed alone as a satisfactory dewaxing solvent liquid. Its selective solvent action as between solid and liquid hydrocarbon constituents of wax-bearing mineral oil, at temperatures of around 0 F., is such that when dewaxing with this solvent liquid the pour temperature of the dewaxed oil will correspond closely to the dewaxing temperature.

In some cases, as for example in the case of relatively heavy viscous oils, such as residual cylinder stocks, it may be desirable to employ a diluent solvent in conjunction with acetal. Accordingly in dewaxing such stocks, the wax-bearing oil may be mixed with a solvent mixture composed of acetal and solvent liquids of the character of benz'ol and its homologs or a light petroleum fraction, such as naphtha, or a petroleum fraction comprising mainly the normally gaseous hydrocarbons, such as propane and butane.

In order to more fully describe the invention, reference will now be made to the following example in which a solvent refined wax-bearing distillate oil derived from Mid-continent crude was dewaxed with acetal:

Gravity A. P. I 26.9 Saybolt universal vis. at 210 F 112 seconds Pour test 120 One volume of the foregoing oil was mixed with four volumes of acetal and the mixture heated to a temperature of about 130 F. to effect solution of the oil in the solvent.

The mixture was then cooled to a temperature of 0 F. to precipitate the wax constituents. While maintained at this temperature the cold mixture was filtered in order to separate the precipitated wax constituents.

The solvent was removed from the resulting filtrate by distillation and the remaining dewaxed oil, amounting to about 80% of the original wax-bearing oil, had a pour test of about F.

The proportion of acetal to oil undergoing dewaxing may vary considerably from that specified in the foregoing example. Thus it is contemplated that the proportion of acetal to oil may be either less or greater than that mentioned. Usually from 2 to 4 volumes of acetal to about one volume of wax-bearing oil provides a suitable dewaxing mix.

In the case of relatively heavy viscous oils where it is desired to use a modifying or diluent solvent as already indicated, the proportion of acetal to diluent solvent will depend to some extent upon the character of the oil undergoing treatment and also upon the nature of the diluent being used. In the case of reduced residual cylinder stocks, for example, the proportion of acetal to diluent liquid may comprise around one part of acetal to 2 or 3 parts of diluent solvent.

The solvent of my invention is adapted to the separation of wax from petroleum oil or from either residual or distillate fractions thereof. It is also adapted to the treatment of wax concentrates for the purpose of effecting the separation between the wax and oil constituents.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may

be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. In the dewaxing of wax-bearing mineral oil, the method which comprises mixing the oil with a solvent comprising acetal, chilling the mixture to precipitate ,wax constituents, and separating the precipitated wax constituents from the cold mixture.

2. In the dewaxing of wax-bearing mineral oil,

the method which comprises mixing the oil with 0 F. and below to precipitate wax constituents,

and removing the precipitated wax constituents from the cold mixture.

4. In the dewaxing of wax-bearing mineral oil, the method which comprises mixing the oil with a solvent liquid comprising a. dialkyl ether having the formula:

OHaCH where R-R represent alkyl radicals selected from the group consisting of methyl, ethyl and propyl, chilling the mixture to precipitate wax constituents, and separating the precipitated Wax constituents from the cold mixture.

EDWIN C. KNOWLES. 

